Before this change, if REPL blocked executing some code, it was possible
to still input new statememts and excuting them, all leading to weird,
and portentially dangerous interaction.
TODO: Current implementation may have issues processing input accumulated
while REPL was blocked.
This is a convenience function similar to pyexec_file. It should be used
instead of raw mp_parse_compile_execute because the latter does not catch
and report exceptions.